Elevator safety codes are being enacted that require that an elevator car be stopped if it moves out of a landing zone while its doors are still open. Thus protection against car movement when the car is at a landing is being sought. Such car movement can happen when control over the traction machine is lost, as when a gear or other part of the machine breaks. U.S. Pat. No. 4,923,055 granted May 8, 1990 to G. A. Holland discloses a mechanism for preventing unintended motion in traction elevators, which mechanism addresses the problems of overspeed and also movement of the car from a landing with the car doors open. The Holland mechanism uses a trigger which is selectively armed when the car is stopped, or when overspeed occurs, and which is tripped by contact with a cam or ratchet tooth on the governor sheave or on the traction sheave. If the trigger is not properly armed, then the mechanism will not operate. Additionally, this device is a fail-safe device which will trip any time the power goes off, thereby requiring frequent manual resetting. There are many delay circuits in the system to prevent false tripping. Finally, the complexity of this patented system prevents a simple retrofit onto existing elevators, since special parts, as for example the special sheaves, must be used.